Rubber hoses of curved shape are required in a variety of applications. Curved or formed hoses are recognized as hoses of finite length, having been shaped along their length to adapt to the particular hose application. Typical examples of applications for curved hoses is in automotive radiators, transmission oil coolers, braking systems, engine oil coolers, power steering systems, and fuel systems. The hoses are curved, or formed, into the shape dictated by the design of the automobile engine compartment, for example, to fit or conform into the area where the hose is to be used. Typically curved hoses may be manufactured by extruding a rubber core layer, applying a reinforcement layer over the core layer, and extruding a cover layer over the reinforcement layer to form an indefinite length hose. The uncured or partially cured hose length is cut to finite lengths and may be placed manually on rigid mandrels having the shape of the desired finished hose configuration. The mandrels and the uncured hose assemblies are placed in vulcanization units. The lengths of hose are vulcanized on the mandrels in the desired configuration. The finished hoses are removed from the mandrels.
This conventional method of manufacturing curved hoses is very labor-intensive. The desired final hose configuration often requires three-dimensional routing of the hose length. The hose lengths are manually inserted onto and removed from the rigid mandrels. For complex curved hoses, more than one person is often required to insert and remove the hose lengths on and off of the rigid mandrels. While mandrel lubricants are employed, loading and unloading the hose may cause the interior walls of the hoses to rip or tear.
One manifestation of the difficulty in manufacturing curved hoses is the level of adhesion of the reinforcement to the innermost rubber core layer and to the rubber cover. During loading and unloading of the hose on the rigid mandrels, the layers may move relative to one another, leading to poor adhesion and ultimately delamination during production, storage or use of the hose. If steam vulcanization is used, steam may migrate between the hose layers along the length of the hose, interfering with the formation of adequate bonding between the layers. In an effort to improve the adhesion between the reinforcement and rubber layers, polyester reinforcement may be pretreated with an isocyanate material. The hose may be partially cured before cutting and placing on the mandrel. The partial curing is intended to impart some degree of bonding between the hose layers, to resist separation or tearing during the shaping process. Finally, the hose ends may be capped with elastic or metallic bands to resist the migration of steam between the hose layers during vulcanization.
Prior art methods for making curved hoses are disclosed in U.S. Pat. Nos. 6,464,916 and 4,242,296 and Japanese Publications 5200900, 4250025, and 4339638. The use of end caps to prevent migration of steam into hose is disclosed in U.S. Pat. No. 3,972,757.
U.S. Pat. No. 5,807,634 discloses a method for improving the adhesion of alkylated chlorosulfonated polyethylene and chlorosulfonated polyethylene rubber to a polyester reinforcement treated with an RFL comprising chlorosulfonated polyethylene.